The present invention relates generally to filter systems, and more particularly to a filtration system for storm water drains for filtering silt from wastewater flowing into street curb drains.
A storm sewer system helps prevent flooding by diverting rain and melted snow into the nearest river or creek through a network of underground pipes. Surface water enters the storm sewer system through curb-side street drains and flows by gravity to the outfalls, where the water is discharged into a creek or river. Since pollutants can enter the storm sewer system through street drains, local waterways can be damaged when debris is carried into the drain along with the surface water. This is a particular problem in areas where new construction is taking place. Regardless of how thoroughly builders may maintain a construction project, silt is likely to accumulate on the streets and is blown into the curb-side street drains, and into the water system, by rain and/or large street-washing trucks.
A street curb drain typically includes a storm water catch basin, a fixed frame with a catch basin inlet and a grate covering the drain opening. Examples of silt catching devices for use with street drains are shown in U.S. Pat. Nos. 4,419,232 and 5,575,925. The devices include a silt filtering bag which is constructed of a fabric designed to capture the silt while allowing the water to flow therethrough. In U.S. Pat. No. 5,575,925, the filter bag includes a plurality of lift flaps which are designed to extend between the grate covering and the catch basin inlet so that the grate covering sandwiches the flaps in place against the catch basin for supporting the filter bag in the catch basin.
One disadvantage of this silt catching device is that it requires the edges of the filter bag to be placed at street level. Thus, the fabric edges of the bag are exposed to vehicular traffic and may become frayed and/or ripped. Whe n the bag is ready to be emptied, there may be no fabric or not enough fabric to handle the weight of the silt-filled bag thereby causing the bag to fall into the drain. In this event, a person must be lowered into the drain and remove the silt with buckets which are passed to people at the street level to clean out the drain. The cleaning out of a silt-filled drain is a difficult and time-consuming task.
Another disadvantage of silt catching devices is that the filter bag may be too deep and too wide for the catch basin. Thus, during a hard rain, the sack may press against the sides of the drain thereby preventing water from passing, through the sack and causing the streets to flood. A further disadvantage of current silt-catching devices is that the design and location of such devices at street level may force silt to build up in the street while affording minimal overflow capabilities during hard rain. Therefore, there is a need for a simple, readily accessible silt trap system which effectively catches the silt and allows the silt to be safely and easily removed.